JP2006039465A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device and an image forming apparatus capable of borderless printing without impairing print quality.
A fixing device includes a fixing roller, a pressure roller that is pressed against the fixing roller, and a release agent supply unit that supplies the release agent to the fixing roller or the pressure roller. It has. When the wax content A (parts by weight) of the toner and the release agent application amount B (mg / sheet) for the fixing roller 1 or the pressure roller 2 satisfy the following expressions (1) to (3): Thus, it is possible to fix a borderless image without causing a fixing failure.
0 ≦ A ≦ 20 (1)
0 ≦ B ≦ 1.0 (2)
8 ≦ (A + 12 × B) ≦ 32 (3)
[Selection] Figure 1

Description

  The present invention relates to a fixing device and an image forming apparatus using the same.

  2. Description of the Related Art Conventionally, image forming apparatuses such as printers and facsimiles use a fixing device that fixes a toner image transferred onto the surface of a recording medium to the recording medium by heating and pressing. As such a fixing device, a heat roller fixing device including a heat roller and a belt fixing device including a heat transfer belt are known. In these fixing devices, a release agent is applied to the surface of the heat roller or the like in order to prevent the recording medium or toner from adhering to the heat roller or heat transfer belt (see, for example, Patent Document 1).

Japanese Patent Laying-Open No. 2003-98884 (see page 3, FIG. 1)

  Here, in recent years, the image forming apparatus is required to support “marginless printing” in which no margin is left on the outer periphery of the recording medium. However, if the margin at the leading end in the conveyance direction of the recording medium is reduced, the recording medium may wrap around without being separated from the heat roller or the like, so a sufficient margin must be ensured at the leading end of the recording medium. In other words, there is a problem that borderless printing cannot be performed. On the other hand, when a large amount of release agent is used to facilitate separation of the recording medium from a heat roller or the like, there is a problem that a large amount of the release agent adheres to the surface of the recording medium and print quality is impaired.

  SUMMARY An advantage of some aspects of the invention is to provide a fixing device and an image forming apparatus that enable borderless printing without deteriorating print quality.

The fixing device according to the present invention includes a fixing member, a heat source that heats the fixing member, a pressure member that is pressed against the fixing member to form a nip portion with the fixing member, and the fixing member or A release agent supplying means for supplying a release agent to the pressure member, and fixing the toner image to the recording medium by pressurizing and heating the recording medium carrying the toner image in the nip portion. In the fixing device, the wax content of the toner is A (parts by weight), and the amount of the release agent applied to the fixing member or the pressure member by the release agent supply unit is determined per sheet of A4 size recording medium. Assuming that B (mg / sheet), the following formulas (1) to (3) are satisfied.
0 ≦ A ≦ 20 (1)
0 ≦ B ≦ 1.0 (2)
8 ≦ (A + 12 × B) ≦ 32 (3)

  According to the present invention, the releasability of the recording medium from the fixing member can be improved without impairing the print quality, and the problem of winding of the recording medium around the fixing member can be solved. As a result, the margin at the front end of the recording medium in the conveyance direction can be eliminated (or limited to a minute range), and borderless printing can be performed.

Embodiments of the present invention will be described below with reference to the drawings.
First Embodiment FIG. 1 is a diagram illustrating a basic configuration of a fixing device according to the present embodiment. This fixing device has a fixing roller 1 and a pressure roller 2 arranged in parallel to each other. The fixing roller 1 is a so-called heat roller having a heat source 3 inside. FIG. 2A is a cross-sectional view showing the structure of the fixing roller 1 (excluding the heat source 3). This fixing roller 1 is provided with an elastic layer 18 around a pipe-shaped cored bar portion 17, and the outer periphery of the elastic layer 18 is covered with a release layer 19. Since the core metal part 17 needs a certain rigidity, it is made of metal (for example, aluminum, iron, stainless steel). The elastic layer 18 is formed of a rubber material having high heat resistance (for example, normal silicon rubber, sponge-like silicon rubber, or fluorine rubber). The release layer 19 is a resin having high heat resistance and low surface free energy after molding, such as polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), perfluoroethylene-propene copolymer (FEP) and the like. Formed of a typical fluorine-based resin. The thickness of the release layer 19 is preferably 10 to 50 μm.

  The pressure roller 2 is pressed against the fixing roller 1 by a pressing mechanism (not shown), and a nip portion is formed between the fixing roller 1 and the pressure roller 2. FIG. 2B is a cross-sectional view showing the structure of the pressure roller 2. The pressure roller 2 is provided with an elastic layer 21 around a pipe-shaped cored bar portion 20. As in the case of the fixing roller 1 described above, the cored bar portion 20 is formed of metal (for example, aluminum, iron, stainless steel). The elastic layer 21 is formed of a rubber material having high heat resistance (for example, normal silicon rubber, sponge-like silicon rubber, or fluorine rubber). When performing double-sided printing, a release layer 19 as shown in FIG. 2A is formed on the outer periphery of the elastic layer 21 of the pressure roller 2.

  The release agent application member 4 is, for example, an application roller or felt impregnated with a release agent, and is disposed so as to contact the fixing roller 1. Alternatively, the release agent application member 4 may be a spray that sprays the release agent on the fixing roller 1 in the form of a spray. Further, the release agent application member 4 may be a member that oozes the release agent from a porous film and applies it to the fixing roller 1. As the mold release agent, dimethyl silicone oil, modified dimethyl silicone oil (one obtained by introducing an organic group into dimethyl silicone oil), fluorine oil, or the like having excellent heat resistance, mold release property and chemical stability is used.

  A temperature detection sensor 5 is disposed so as to contact the surface of the fixing roller 1. The temperature detection sensor 5 detects the surface temperature of the fixing roller 1 and transmits a detection signal to a control unit (not shown).

  Examples of the binder resin used in the toner include homopolymers of styrene and its substitutes (for example, polystyrene, poly p-chlorostyrene, polyvinyltoluene), and styrene copolymers (for example, styrene / p-chlorostyrene copolymer). Polymer, styrene / propylene copolymer, styrene / vinyl toluene copolymer, styrene / vinyl naphthalene copolymer, styrene / methyl acrylate copolymer, styrene / ethyl acrylate copolymer, styrene / butyl acrylate copolymer Polymer, styrene / octyl acrylate copolymer, styrene / methyl methacrylate copolymer, styrene / ethyl methacrylate copolymer, styrene / butyl methacrylate copolymer, styrene / α-chloromethyl methacrylate copolymer , Styrene / acrylonitrile copolymer, styrene / vinyl methacrylate Luketone copolymer, styrene / butadiene copolymer, styrene / isoprene copolymer, styrene / maleic acid copolymer), acrylate ester homopolymers and their copolymers (eg, polymethyl acrylate, polyacrylic) Acid butyl, polymethyl methacrylate, polybutyl methacrylate), polyvinyl derivatives (eg, polyvinyl chloride, polyvinyl acetate), polyester-based polymers, polyurethane-based polymers, polyamide-based polymers, polyimide-based polymers, polyol-based polymers Polymers, epoxy polymers, terpene polymers, aliphatic or alicyclic hydrocarbon resins, aromatic petroleum resins and the like can be used alone or in combination. From the viewpoints of binding properties and electrical characteristics, it is preferable to contain at least one of styrene-acrylic copolymer resin, polyester resin and polyol resin.

  In some cases, the toner contains a wax for the purpose of preventing offset at the time of fixing. In this case, waxes such as polyethylene wax, propylene wax, carnauba wax, and various ester types can be used. The melting point of the wax is preferably 50 to 140 ° C. This is because when the melting point of the wax is less than 50 ° C., the wax is detached or exuded from the toner surface, and when the melting point of the wax exceeds 140 ° C., sufficient offset resistance cannot be obtained. The melting point of the wax is more preferably 60 to 130 ° C, particularly preferably 70 to 120 ° C.

  As the colorant used in the toner, pigments and dyes conventionally used as toner colorants can be used. Specifically, carbon black, lamp black, iron black, ultramarine, nigrosine dye, pigment yellow, pigment red, pigment blue, aniline blue, phthalocyanine blue, phthalocyanine green, Hansa Yellow G, rhodamine 6C lake, calco oil blue, chrome Yellow, quinacridone red, benzidine yellow, rose bengal and the like can be used alone or in combination.

  In addition, a generally known charge control agent can be used for the toner in order to improve the rising of charging. Specifically, positively chargeable charge control agents (for example, amino group-containing vinyl copolymers, quaternary ammonium salt compounds, nigrosine dyes, polyamine resins, imidazole compounds, azine dyes, triphenylmethane materials, guanidine compounds, lakes). Pigments) or negatively chargeable charge control agents (for example, carboxylic acid derivatives and metal salts thereof, alkoxylates, organometallic complexes, chelate compounds) can be used alone or in combination. When a negatively chargeable charge control agent is used, it is particularly preferable to use a metal salt of a salicylic acid derivative as an additive in order to obtain stable charge rising characteristics.

  Inorganic powders (for example, silica, zinc oxide, tin oxide, aluminum oxide, titanium oxide, silicon oxide, strontium titanate, barium titanate, calcium titanate as additives for improving the fluidity and environmental dependency of the toner Strontium zirconate, calcium zirconate, lanthanum titanate, calcium carbonate, magnesium carbonate, mica, dolomite) or a hydrophobized product thereof can be used alone or in combination. In addition, fluororesin fine particles (for example, polytetrafluoroethylene, tetrafluoroethylene hexafluoropropylene copolymer, polyvinylidene fluoride) may be used as the toner surface modifier. About 0.1 to 10 parts by weight are externally added to 100 parts by weight of the toner base particles, and if necessary, they are mixed by an appropriate mixer to adhere and adhere to the toner particle surface. It can adjust so that it may be in a free state.

  The operation of the fixing device shown in FIG. 1 is as follows. As described above, the pressure roller 2 is pressed against the fixing roller 1, and a nip portion is formed between the fixing roller 1 and the pressure roller 2. A control unit (not shown) drives and controls the heat source 3 based on a temperature detection signal from the temperature detection sensor 5 to maintain the surface temperature of the fixing roller 1 at an appropriate temperature. The release agent application member 4 applies a release agent to the surface of the fixing roller 1 (release layer 19). This release agent is held on the unevenness of the surface having a predetermined surface roughness of the release layer 19 of the fixing roller 1. FIG. 2C is an enlarged view showing a nip portion between the fixing roller 1 and the pressure roller 2. Since the pressure roller 2 is pressed against the fixing roller 1, the elastic layer 18 of the fixing roller 1 is deformed so as to be recessed near the nip portion.

  On the surface of the recording medium 6 (for example, A4 copy paper), toner (indicated by reference numeral 7 in FIG. 1) is transferred by a transfer unit (not shown) of the image forming apparatus. The recording medium 6 carrying the unfixed toner is conveyed through a nip portion between the fixing roller 1 and the pressure roller 2 and is heated and pressed by the fixing roller 1 and the pressure roller 2, whereby the toner 7 is fixed to the recording medium 6. The recording medium 6 is separated without being wound around the fixing roller 1. The recording medium 6 is reliably separated from the fixing roller 1 because (1) the radius of curvature at the end of the nip portion in the transport direction is very small compared to the radius of the fixing roller 1, and (2) the fixing roller 1 The release layer 19 has a high release property, (3) the release agent is applied to the surface of the release layer 19 by the release agent application member 4, and (4) the toner 7. This is due to a synergistic effect of the fact that the wax is contained.

  Next, a fixing device using a belt will be described. FIG. 3A is a diagram illustrating a basic configuration of a fixing device using a belt. The fixing device includes a fixing roller 8, a heating roller 11, and a fixing belt 12 that is stretched over the fixing roller 8. Inside the heating roller 11, a heat source 10a is provided. A pressure roller 9 having a heat source 10 b therein is pressed against the fixing roller 8 via a fixing belt 12. A temperature detection sensor 13 for detecting the surface temperature of the fixing belt 12 is disposed so as to be in contact with the surface of the fixing belt 12. Further, a release agent application member 14 for applying a release agent to the fixing belt 12 is disposed so as to be in contact with the surface of the fixing belt 12.

  The fixing roller 8 and the pressure roller 9 are provided with an elastic layer 21 around a pipe-shaped cored bar portion 20 in the same manner as the pressure roller 2 shown in FIG. The core metal part 20 is made of metal (for example, aluminum, iron, stainless steel), and the elastic layer 21 is made of a rubber material having high heat resistance (for example, normal silicon rubber, sponge-like silicon rubber, fluoro rubber). Is formed. The heating roller 11 incorporating the heat source 10a is configured by a pipe made of metal (for example, aluminum, iron, stainless steel).

  FIGS. 3B and 3C are cross-sectional views illustrating a configuration example of the fixing belt 12. In the fixing belt 12, as in the configuration example shown in FIG. 3B, an elastic layer 22b made of silicon rubber or fluorine resin is formed on a thin base 22a, and a release layer 22c is formed thereon. Can be configured. When the base 22a is made of nickel, polyimide, stainless steel, or the like, the thickness of the base 22a is preferably 30 to 150 μm. The thickness of the elastic layer 22b is preferably 50 to 300 μm in the case of silicon rubber, and preferably 10 to 50 μm in the case of a fluororesin. Further, as shown in FIG. 3C, the fixing belt 12 may be configured by forming a release layer 22c on a thin substrate 22a. 3B and 3C, the fixing belt 12 is wound around the fixing roller 8 and the heating roller 11 with the release layer 22c side facing outside.

  The release layer 22c of the fixing belt 12 is a resin having high heat resistance and low surface free energy, such as, for example, polytetrafluoroethylene (PTFE), perfluoro, like the release layer 19 shown in FIG. It is made of a typical fluorine resin such as alkoxyalkane (PFA) or perfluoroethylene-propene copolymer (FEP). The thickness of the release layer 22 is preferably 10 to 50 μm. Further, the surface of the release layer 22 c of the fixing belt 12 is provided with a certain surface roughness for holding the release agent supplied from the release agent application member 14.

  The configurations of the release agent application member 14, the temperature detection sensor 13, the toner 16 and the recording medium 15 are the same as those of the release agent application member 4, the temperature detection sensor 5, the toner 7 and the recording medium 6 described with reference to FIG. Are the same.

  The operation of the fixing device shown in FIG. 3 is as follows. The pressure roller 9 is pressed against the fixing roller 8 via the fixing belt 12, and a nip portion is formed between the fixing belt 12 and the pressure roller 9. A control unit (not shown) drives and controls the heat sources 10a and 10b based on the temperature detection signal from the temperature detection sensor 13, and maintains the surface temperature of the fixing belt 12 at an appropriate temperature. The release agent application member 14 applies a release agent to the surface (release layer 22 c) of the fixing belt 12. This release agent is held on the unevenness of the surface of the release layer 22 c of the fixing belt 12. The recording medium 15 onto which the toner 16 has been transferred in a transfer portion (not shown) of the image forming apparatus is conveyed through a nip portion between the fixing belt 12 and the pressure roller 9, and is heated and heated by the fixing belt 12 and the pressure roller 9. The toner 16 is fixed to the recording medium 15 by being pressurized. As described with reference to FIG. 1, the recording medium 15 is separated without being wound around the fixing belt 12.

  Next, in order to find out the conditions for enabling borderless printing, the results of experiments for each parameter will be described. Here, the relationship between the adhesion force of the recording medium to the fixing roller 1 (the force necessary for peeling the recording medium from the fixing roller 1, also referred to as peeling resistance) and the wax content in the toner, the recording medium is fixed to the fixing roller 1. Experiments were conducted on the relationship between the margin (necessary margin) necessary for separation from the adhesive and the adhesive force, and the contribution of the surface roughness of the fixing roller 1 and the amount of release agent applied to the adhesive force and the required margin.

  FIG. 4 schematically shows a method for measuring the adhesive force. The recording medium 6 (A4 size) is conveyed in the short side direction, passed through the nip portion between the fixing roller 1 and the pressure roller 2, and the recording medium 6 is intentionally wound around the fixing roller 1, so that the recording medium 6 The driving of the fixing device is temporarily stopped when the tip of the toner reaches the position rotated 90 degrees from the nip portion. In this state, a plate-like holder 6a having a length of 297 mm (same as the length of the recording medium 6) and a width of 5 mm along the front end of the recording medium 6 is also used, and a double-sided tape having a length of 297 mm and a width of 5 mm. Paste using 6b. Further, using the tension gauge, the longitudinal direction center of the holder 6a is peeled vertically (that is, the recording medium 6 is peeled from the fixing roller 1 so that the increase rate of the tension is 100 gf / s (= 0.98 N / s). The tension at the moment when the recording medium 6 is peeled off is read. Note that the measurement results may be affected by the fixing temperature, the recording medium conveyance speed, or the tension gauge tension speed. Therefore, it was judged that there was no problem in terms of reproducibility. The data of the adhesion force of each graph to be described later is an average of 10 times.

  The fixing roller 1 used for measuring the adhesive force has a release layer made of a 30 μm thick PFA tube on the outer periphery of a cored bar made of a 36 mm diameter aluminum pipe (thickness 1.5 mm). The elastic layer is not provided. The surface roughness Rz of the release layer is 0.2 μm. The Asker C hardness on the surface of the fixing roller 1 is 95 degrees. The pressure roller 2 is provided with an elastic layer (2.0 mm thick) made of silicon rubber on the outer periphery of a cored bar made of an aluminum pipe (thickness 1.5 mm) having a diameter of 36 mm, and further a PFA having a thickness of 30 μm. A release layer made of a manufactured tube is provided. The surface roughness Rz of the release layer is 0.2 μm. The Asker C hardness on the surface of the pressure roller 2 is 70 degrees.

In the measurement of the adhesion force, the pressing force of the pressure roller 2 against the fixing roller 1 is 30 kgf (= 294 N). As the toner, an emulsion polymerization toner of each color (yellow, magenta, cyan) is used. The wax content in the toner is 0 to 40 parts by weight. The recording medium is A4 size, and the weight per unit area is 64 g / m ² . The transfer toner amount per recording medium is 1.5 ± 0.1 g / sheet. The conveyance speed of the recording medium passing between the fixing roller 1 and the pressure roller 2 is 100 mm / s, and the conveyance direction is the short direction (so-called lateral feed) of the recording medium. The surface temperature of the fixing roller 1 is 160 ° C., and the surface temperature of the pressure roller 2 is 130 ° C. As the release agent, dimethyl silicon having a kinematic viscosity of 300 cSt (= 300 cm ² / s) is used, and the coating amount per recording medium is 0 to 6 mg / sheet. In addition, the release agent is applied to the fixing roller 1 by bringing an application roller having a porous surface layer impregnated with the release agent into contact with the surface of the fixing roller 1.

In this case, as a generally used copy paper, a 64 g / m ² recording medium belonging to a thin class is used, but this is for evaluating the adhesive force under more severe conditions. The transfer toner amount was adjusted so as to obtain the maximum density when the three colors of yellow, magenta, and cyan were superimposed. Further, the toner was uniformly transferred to the whole so that there was no margin at the front end portion in the transport direction of the recording medium 6 (width 0 mm) and a margin of 5 mm width was formed at the rear end portion in the transport direction. A slight offset occurred when the adhesive force was 700 gf (= 6.9 N) or more, but the measured value was adopted as it was.

The production of the toner by the emulsion polymerization method is as follows.
(1) Generate primary particles of a polymer which is a binder resin for a toner in an aqueous solvent. Here, primary particles made of a styrene-acrylic copolymer resin are produced from styrene, acrylic acid, and methylmethacrylic acid in an aqueous solvent.
(2) Subsequently, a colorant emulsified with an emulsifier (surfactant) is mixed in the same solvent as the primary particles, and a wax, a charge control agent, and the like are mixed as necessary. Here, Pigment Yellow 74 is used as a yellow colorant, Pigment Red 238 is used as a magenta colorant, and Pigment Blue 15: 3 is used as a cyan colorant. As the wax, stearyl stearate which is a higher fatty acid ester wax is used. Further, in order to ensure the fluidity of the toner, 1 to 3 parts by weight of silica having a particle size of 8 to 20 nm is added.
(3) By aggregating them, toner particles are formed in the solvent. The toner particles are obtained by removing the unnecessary solvent components and by-product components from the solvent and washing and drying.

  The measurement result of the adhesive force under the above conditions will be described. FIG. 5 is a graph showing the relationship between the adhesive force and the wax content in the toner while changing the amount of the release agent applied. The amount of the release agent applied is evaluated by the weight of the release agent per A4 size recording medium. This is because the nip portion between the fixing roller 1 and the pressure roller 2 is 1000 sheets. This is calculated from the change in the weight of the release agent application member 4 after passing through the recording medium. Here, the application amount of the release agent was changed in five ways: 0 mg / sheet, 0.05 mg / sheet, 0.5 mg / sheet, 5.0 mg / sheet, 6.0 mg / sheet.

  From the graph of FIG. 5, it can be seen that the decrease in adhesion is almost flat when the wax content in the toner is 20 parts by weight or more for any of the release agent coating amounts of 0 to 6 mg / sheet. From this, it can be seen that a wax content in the toner of 20 parts by weight is sufficient to obtain the effect of reducing the adhesive force. That is, a preferable range of the wax content A (parts by weight) in the toner is 0 ≦ A ≦ 20. In order to reduce toner aggregation and filming in the developing device when left for a long period of time, the wax content in the toner is preferably as low as possible. This is a problem that can be solved and does not limit the range of the wax content described above.

  Further, from FIG. 5, the adhesive force is almost equal to 100 gf (= 0.98 N) when the release agent application amount is 5 mg / sheet and 6 mg / sheet, and even if the release agent application amount further increases. The wearing force is considered to be almost flat at 100 gf. From this, the lower limit of the adhesive force is considered to be 100 gf.

  FIG. 6 shows the relationship between the margin (necessary margin) necessary to separate the front end of the recording medium from the fixing roller 1 and the adhesive force when the hardness difference between the fixing roller 1 and the pressure roller 2 is changed. It is a graph. In FIG. 6, the value (hardness difference) obtained by subtracting the Asker C hardness of the fixing roller 1 from the Asker C hardness of the pressure roller 2 is changed in four ways: 25 degrees, 10 degrees, 0 degrees, and −20 degrees. . Here, instead of forming a margin at the front end of the recording medium in the conveyance direction, the margin at the rear end of the recording medium in the conveyance direction is reduced by that amount so that the transfer area becomes constant. In FIG. 6, the “necessary margin” of the recording medium means that the recording medium is passed through the nip portion between the fixing roller 1 and the pressure roller 2 five times under the same conditions, and the leading end of the recording medium is removed from the fixing roller 1 both times This is the margin (the width from the leading end in the conveyance direction of the recording medium to the printing area) when it can be separated.

  The fixing roller 1 used in this measurement is provided with an elastic layer made of silicon rubber (thickness 2.0 mm) on the outer periphery of a cored bar made of aluminum pipe (thickness 1.5 mm) having a diameter of 36 mm, and further thickened. A release layer composed of a PFA tube having a thickness of 30 μm is provided. The surface roughness Rz of the release layer is 0.2 μm. The Asker C hardness on the surface of the fixing roller 1 is 70 degrees. The pressure roller 2 is provided with an elastic layer (thickness 0 to 2.0 mm) made of silicon rubber on the outer periphery of a cored bar portion made of an aluminum pipe (thickness 1.5 mm) having a diameter of 36 mm, and further has a thickness of 30 μm. A release layer composed of a PFA tube is provided. The surface roughness Rz of the release layer is 0.2 μm. By varying the thickness of the elastic layer in three ways in the range of 0 to 2.0 mm, the Asker C hardness is varied in three ways: 70 degrees, 80 degrees, and 95 degrees. Note that another type of pressurizing roller 2 (having Asker C hardness smaller than that of the fixing roller 1) is prepared. In this example, an elastic layer (thickness 6.0 mm) made of silicon sponge is provided on the outer periphery of a cored bar portion made of a stainless steel shaft having a diameter of 36 mm. The surface roughness Rz of the release layer is 0.2 μm, and the Asker C hardness on the surface of the pressure roller 2 is 50 degrees.

The pressing force of the pressure roller 2 against the fixing roller 1 is 30 kgf. As the toner, an emulsion polymerization toner of each color (yellow, magenta, cyan) is used. The wax content in the toner is 0 to 20 parts by weight. The recording medium is A4 size, and the weight per unit area is 64 g / m ² . The transfer toner amount per recording medium is 1.5 ± 0.1 g / sheet. The conveyance speed of the recording medium passing through the nip portion between the fixing roller 1 and the pressure roller 2 is 100 mm / s, and the conveyance direction is the short direction of the recording medium. The surface temperature of the fixing roller 1 is 160 ° C., and the surface temperature of the pressure roller 2 is 130 ° C. As the release agent, dimethyl silicon having a kinematic viscosity of 300 cSt is used, and the coating amount per recording medium is 0 to 6 mg / sheet. In addition, the release agent is applied to the fixing roller 1 by bringing an application roller having a porous surface layer impregnated with the release agent into contact with the surface of the fixing roller 1.

  The reason why the thickness of the elastic layer made of silicon rubber of the fixing roller 1 is 2 mm is that the heat resistance and the heat capacity increase as the elastic layer becomes thicker, so that the rise time is delayed and overshoot and undershoot are remarkable. This is because temperature control may become difficult. If the thickness is 2 mm or less, such a problem does not occur.

  From the graph of FIG. 6, it can be seen that the greater the adhesion, the greater the required margin of the recording medium (that is, the separation is not separated from the fixing roller 1 unless the margin is increased). Furthermore, it can be seen that the larger the difference in hardness obtained by subtracting the Asker C hardness of the fixing roller 1 from the Asker C hardness of the pressure roller 2, the smaller the necessary margin even when the adhesive force is large.

  Here, if the difference in hardness obtained by subtracting the Asker C hardness of the fixing roller 1 from the Asker C hardness of the pressure roller 2 is −20 degrees, a margin of 2 mm is required even if the adhesive force is 100 gf, which is the lower limit. For this reason, it is considered that it is not suitable for the purpose of completely setting the margin to 0 mm. However, so-called “marginless printing” does not necessarily mean that no margin is left, and even if there is a margin of 2 mm from the leading end of the recording medium in the conveyance direction, it may be recognized as “marginless printing”. . In this case, even if the hardness difference is −20 degrees, the object can be achieved.

  In addition, considering that the Asker C hardness is about 95 degrees when a release layer is formed directly on an aluminum pipe (without forming an elastic layer), considering that a higher hardness is not practical, The Asker C hardness C (degree) of the fixing roller 1 is preferably in the range of 70 ≦ C ≦ 95. The difference in hardness obtained by subtracting the Asker C hardness C of the fixing roller 1 from the Asker C hardness D of the pressure roller 2 is preferably in the range of −20 ≦ D−C ≦ 25.

From FIG. 6, in order for the hardness difference to be within a range of -20 degrees to 25 degrees and the necessary margin to be within 2 mm, the adhesive force is 100 gf (= 0.98 N) or more and 450 gf (= 4.41 N) or less. I understand that it is necessary. Further, from FIG. 5, it is assumed that the wax content of the toner is A (parts by weight), and the amount of release agent applied to the fixing roller release layer (per A4 size recording medium) is B (mg / sheet). When the following expression is satisfied, it can be seen that the adhesive force is 100 gf or more and 450 gf or less.
8 ≦ A + 12 × B ≦ 80

  FIG. 7 is a graph showing changes in fixing characteristics with respect to the surface roughness of the release layer of the fixing roller 1 and the amount of release agent applied. The fixing roller 1 used in this measurement is provided with an elastic layer having a thickness of 2.0 mm made of silicon rubber on the outer periphery of a cored bar portion made of an aluminum pipe (thickness 1.5 mm) having a diameter of 36 mm, and further having a thickness. A release layer comprising a 30 μm PFA tube is provided. The release layer has a surface roughness Rz of 0.2 to 0.7 μm. The Asker C hardness on the surface of the fixing roller 1 is 70 degrees. The pressure roller 2 has a release layer made of a PFA tube having a thickness of 30 μm on the outer periphery of a cored bar portion 20 made of an aluminum pipe (thickness 1.5 mm) having a diameter of 36 mm, without an elastic layer. It is provided. The surface roughness Rz of the release layer is 0.2 μm. The Asker C hardness on the surface of the pressure roller 2 is 95 degrees.

The pressing force of the pressure roller 2 against the fixing roller 1 is 30 kgf. As the toner, an emulsion polymerization toner of each color (yellow, magenta, cyan) is used. The wax content in the toner is 8 parts by weight. The recording medium is A4 size, and the weight per unit area is 64 g / m ² . The transfer toner amount per recording medium is 1.5 ± 0.1 g / sheet. The toner transfer is performed so that a margin of 2 mm width is formed at the front end of the recording medium in the conveyance direction. The conveyance speed of the recording medium passing through the nip portion between the fixing roller 1 and the pressure roller 2 is 100 mm / s, and the conveyance direction is the short direction of the recording medium. The surface temperature of the fixing roller 1 is 160 ° C., and the surface temperature of the pressure roller 2 is 130 ° C. As the release agent, dimethyl silicon having a kinematic viscosity of 300 cSt is used, and the coating amount per recording medium is 0 to 6 mg / sheet. In addition, the release agent is applied to the fixing roller 1 by bringing an application roller having a porous surface layer impregnated with the release agent into contact with the surface of the fixing roller 1.

  Here, the reason that the Asker C hardness of the fixing roller 1 and the pressure roller 2 is set to 70 degrees and 95 degrees, respectively, is to make the adhesion force the upper limit value 450 gf of the optimum range (100 to 450 gf). is there. The reason why the wax content of the toner is 8 parts by weight is that the adhesive force is 450 gf even when the release agent coating amount is 0 mg / sheet. As the release layer of the fixing roller 1, a PFA tube that is uniformly polished with a lapping sheet and baked at 350 ° C. for 3 hours is used.

  Printing is performed under such conditions, and it is possible to fix a borderless image (a toner image transferred so that the margin at the front end of the recording medium in the conveyance direction is 2 mm or less) and fixing failure ( The presence / absence of offset, flashing and unevenness was examined. The result is shown in FIG. From FIG. 7, the condition for fixing the borderless image and preventing the fixing failure is that the surface roughness Rz of the release layer of the fixing roller 1 is 5.0 μm or less, and the separation to the fixing roller 1 is performed. It can be seen that the mold application amount B is 5.0 mg / sheet or less and Rz / B is 1.0 or less.

When the experimental results of FIGS. 5 to 7 described above are comprehensively judged, the wax content A (parts by weight) in the toner, the release agent coating amount B (mg / sheet: per A4 size sheet) to the fixing roller. ), The surface roughness Rz (μm) of the fixing roller 1, the Asker C hardness C on the surface of the fixing roller 1, and the Asker C hardness D on the surface of the pressure roller 2, the following expressions (a1) to ( When a7) is established, it can be seen that the borderless image can be fixed and no fixing failure occurs.
0 ≦ A ≦ 20 (a1)
0 ≦ B ≦ 5.0 (a2)
8 ≦ A + 12 × B ≦ 80 (a3)
0 <Rz ≦ 5.0 (a4)
0 <Rz / B ≦ 1.0 (a5)
70 ≦ C ≦ 95 (a6)
−20 ≦ D−C ≦ 25 (a7)

Here, the surface roughness Rz of the release layer of the fixing roller 1 has a great influence on the print image quality, and when the surface roughness Rz exceeds 1 μm, the printing surface is “raised” and the glossiness is preferred. Not suitable for printing (photographs, posters, etc.). Therefore, the surface roughness Rz of the release layer of the fixing roller 1 is preferably 1.0 μm or less. In consideration of this point, it can be seen from FIG. 7 that the release agent coating amount B is 1.0 mg within a range in which a borderless image can be fixed and fixing failure does not occur even when the surface roughness Rz is 1.0 μm or less. Per sheet. Further, from FIG. 5, even when the release agent coating amount B is 1.0 mg / sheet or less, the adhesive force is 100 to 450 gf in the range of 8 ≦ A + 12 × B ≦ 32. From the above, in order to ensure good print quality, equations (a2), (a3), and (a4) can be rewritten as follows.
0 ≦ B ≦ 1.0 (a2 ′)
8 ≦ A + 12 × B ≦ 32 (a3 ′)
0 <Rz ≦ 1.0 (a4 ′)

In summary, the following formula is obtained as a range in which a borderless image can be fixed, fixing failure does not occur, and glossy printing can be handled.
0 ≦ A ≦ 20 (1)
0 ≦ B ≦ 1.0 (2)
8 ≦ A + 12 × B ≦ 32 (3)
0 <Rz ≦ 1.0 (4)
0 <Rz / B ≦ 1.0 (5)
70 ≦ C ≦ 95 (6)
−20 ≦ D−C ≦ 25 (7)

  As described above, according to the fixing device according to the present embodiment, the above-described formulas (1) to (7) are satisfied, so that borderless printing can be performed and fixing defects do not occur. . In addition, there is no “grayness” on the printed surface, and glossy images such as photographs and posters can be formed.

  Equations (1) to (7) are obtained by comprehensively determining the experimental results of FIGS. 5 to 7 and relate to the wax content A and the release agent coating amount B in the toner. Expressions (1) to (3) are considered to be the most important in enabling fixing of a borderless image. In addition, it is possible to form a glossy image by satisfying the formulas (4) and (5), and further, satisfying the formulas (6) and (7) An effect is obtained that a fixing roller or a pressure roller can be used.

  Here, although the experimental results for the fixing device having the fixing roller 1 and the pressure roller 2 as shown in FIG. 1 have been described, the fixing device having the fixing belt 12 as shown in FIG. By satisfying the above formulas (1) to (7), borderless printing with good print quality becomes possible. In this case, the Asker C hardness C is a hardness measured on the surface (fixing surface) of the fixing belt 12 wound around the fixing roller 8. The release agent application amount B is the release agent application amount to the fixing belt 12 by the release agent application member 14, and the surface roughness Rz is the surface roughness of the release layer of the fixing belt 12.

Second Embodiment FIG. 8 is a diagram illustrating a main part of a fixing device according to a second embodiment. This fixing device has a separation / contact mechanism for bringing the release agent application member 26 into contact with and separating from the fixing roller 1. The fixing roller 1 is the same as that described in the first embodiment (FIG. 1), and the heat source 3 is disposed inside thereof. The release agent application member 26 is, for example, an application roller impregnated with a release agent, and is disposed so as to come into contact with the fixing roller 1. Alternatively, the release agent application member 26 may be an application roller that applies the release agent by spreading it from a porous film, and may be disposed so as to contact the fixing roller 1. As the mold release agent, dimethyl silicone oil, modified dimethyl silicone oil, fluorine oil, or the like having excellent heat resistance, mold release property and chemical stability is used.

  The release agent application member 26 is rotatably supported by the support body 27. The support 27 is supported so as to be swingable about a support shaft 28 fixed to a casing (not shown) of the fixing device. The support 27 is urged toward the fixing roller 1 by the pressing spring 25, whereby the release agent application member 26 is pressed against the fixing roller 1 with a predetermined pressing force. The pressing spring 25 is fixed to the tip of the plunger of the solenoid 23. The solenoid 23 drives the plunger toward and away from the fixing roller 1 as indicated by an arrow in the figure. The drive control of the solenoid 23 is performed by the control unit 29. When the solenoid 23 is energized, the plunger protrudes, and the release agent application member 26 swings around the fulcrum 28 and is pressed against the fixing roller 1. When the solenoid 23 is not energized, the plunger retracts and the release agent application member 26 is separated from the fixing roller 1. Further, a stabilizing spring (tensile spring) 24 is attached to the support body 27. The stabilizing spring 24 has a smaller spring constant than the pressing spring 25, one end is fixed to a housing (not shown) of the fixing device, and the support 27 is pulled at the other end. The stabilization spring 24 is provided to stably hold the pressing spring 25 and the support body 27 when the solenoid 23 is not energized.

  In the fixing device according to the present embodiment, when fixing a borderless image (that is, a toner image transferred so as not to leave a margin on the outer periphery of the recording medium), the release agent coating member 26 is used by a separation / contact mechanism. Is fixed to the fixing roller 1 to fix a normal toner image (that is, a toner image transferred with at least a margin at the front end in the conveyance direction) of the recording medium by a release / contact mechanism. The application member 26 is separated from the fixing roller 1. A specific example of the operation of the fixing device in the present embodiment will be described below.

  FIG. 9A is a timing chart showing the operation of the fixing device when a borderless image is printed first and then a normal image is printed. In the initial state (the state before the fixing roller 1 rotates), the solenoid 23 is not energized, and the release agent application roller 26 is separated from the fixing roller 1. From this state, first, the fixing roller 1 starts rotating, then the solenoid 23 is energized, and the release agent application member 26 contacts the fixing roller 1. Thereby, application of the release agent to the fixing roller 1 by the release agent application member 26 is started. After that, the recording medium on which the borderless image is transferred passes through the nip portion between the fixing roller 1 and the pressure roller 2 (FIG. 1), and the borderless image is fixed. Simultaneously with the end of fixing, the energization of the solenoid 23 is stopped, and the release agent applying member 26 is separated from the fixing roller 1. The fixing operation for the second and subsequent pages is performed without driving the solenoid 23.

  FIG. 9B is a timing chart showing the operation of the fixing device when a normal image is printed first, then a borderless image is printed, and then a normal image is printed. In this case, the fixing roller 1 starts rotating in a state where the release agent applying member 26 and the fixing roller 1 are separated from each other, and then the recording medium on which the normal image is transferred is the fixing roller 1 and the pressure roller 2. The normal image is fixed. Simultaneously with the end of fixing, the solenoid 23 is energized and the release agent application member 26 contacts the fixing roller 1. Thereby, application of the release agent to the fixing roller 1 by the release agent application member 26 is started. After that, the recording medium on which the borderless image is transferred passes between the fixing roller 1 and the pressure roller 2, and the borderless image is fixed. Simultaneously with the end of fixing, the energization of the solenoid 23 is stopped, and the release agent applying member 26 is separated from the fixing roller 1. The fixing operation for the third and subsequent pages is performed without driving the solenoid 23.

  FIG. 9C is a timing chart showing an operation when printing a borderless image and then stopping printing. In this case, first, the fixing roller 1 starts rotating in a state where the release agent application member 26 and the fixing roller 1 are separated from each other, and then the solenoid 23 is energized so that the release agent application member 26 contacts the fixing roller 1. Touch. Thereby, application of the release agent to the fixing roller 1 by the release agent application member 26 is started. After that, the recording medium on which the borderless image is transferred passes between the fixing roller 1 and the pressure roller 2, and the borderless image is fixed. Simultaneously with the end of the fixing, the energization of the solenoid 23 is stopped, the release agent applying member 26 is separated from the fixing roller 1, and the rotation of the fixing roller 1 is also stopped at the same time.

  FIG. 10 shows the experimental results comparing the case where the release agent application member 26 is provided with the release contact mechanism and the case where the release agent application member 26 is not provided. When the borderless image and the normal image are printed alternately, the release is performed. The relationship between the amount of the release agent remaining on the agent application member 26 and the number of printed sheets is shown. From FIG. 10, it can be seen that the remaining amount of the release agent at the completion of printing 300,000 sheets when the separation / contact mechanism is provided is the remaining amount of the release agent at the completion of printing 80,000 sheets without the separation / contact mechanism. It turns out that it is the same as quantity. This is because when the separation mechanism is not provided, the release agent oozes from the release agent application member 26 to the fixing roller 1 little by little when printing is interrupted or left, whereas the separation mechanism This is considered to be because it is possible to suppress consumption due to such a bleeding out of the release agent.

  As described above, in the present embodiment, the release agent coating member 26 is separated from the fixing roller 1 except when printing a borderless image. The consumption of the mold can be reduced, and the life of the release agent application member 26 can be extended.

Third Embodiment FIG. 11 is a diagram illustrating a basic configuration of an image forming apparatus according to a third embodiment. As described in the first embodiment, this image forming apparatus is selectively mounted with a fixing device capable of fixing a borderless image and a normal fixing device (not compatible with fixing of a borderless image). It is configured to be able to. Furthermore, in the present embodiment, the fixing device 30 has an instruction unit 31 that indicates whether the fixing device can fix a borderless image or a normal fixing device. The image forming apparatus includes a detection unit 32 that detects the instruction unit 31 and outputs a detection signal, a determination unit 33 that determines the type of the fixing device 30 based on the detection signal, and an image based on the determination result of the determination unit 33. And a control unit 34 that performs drive control of the forming apparatus. 12 to 17 show specific configuration examples of the instruction unit 31 and the detection unit 32. FIG.

  In the configuration example shown in FIGS. 12A and 12B, the instruction section 31 has a pair of protrusions 36a and 36b, and the instruction section 32 has switches 35a and 35b facing the protrusions 36a and 36b. The switches 35a and 35b are mechanical switches that are energized or de-energized when pressed, and are preferably not locked when pressed. As shown in FIG. 12A, when the projections 36a and 36b are both short and the switches 35a and 35b are not pressed by the projections 36a and 36b, an off signal is output from both the switches 35a and 35b. On the other hand, as shown in FIG. 12B, when one protrusion 36a is long and only the switch 35a is pressed, an on signal is output from the switch 35a and an off signal is output from the switch 35b.

  In the configuration example shown in FIGS. 13A and 13B, the indicator 31 has a pair of recesses 38a and 38b, and the indicator 32 has switches 37a and 37b facing the recesses 38a and 38b. The switches 37a and 37b are mechanical switches that are energized or de-energized when pressed, and are preferably not locked when pressed. When the recesses 38a and 38b are both deep and the switches 37a and 37b are not pressed by the recesses 38a and 38b as shown in FIG. 13A, an off signal is output from both the switches 37a and 37b. The On the other hand, as shown in FIG. 13B, when one recess 38a is shallow and only the switch 37a is pressed, an on signal is output from the switch 37a and an off signal is output from the switch 37b.

  In the configuration example illustrated in FIGS. 14A and 14B, the instruction unit 31 includes a light emitting element 39 and a light receiving element 40, and the instruction unit 32 includes a light shielding unit 41. As the light emitting element 39, for example, a light emitting diode or a light bulb can be used. As the light receiving element 40, for example, a photodiode, a phototransistor, a cadmium cell, or a solar battery can be used. As shown in FIG. 14A, when the length of the light shielding portion 41 is sufficiently long, the optical path between the light emitting element 39 and the light receiving element 40 is blocked, and thus the light intensity detected by the light receiving element 40 is set in advance. Below the value. On the other hand, as shown in FIG. 14B, when the length of the light shielding portion 41 is short, the light path is not blocked, and thus the light intensity detected by the light receiving element 40 exceeds a preset value.

  In the configuration example shown in FIGS. 15A and 15B, the instruction unit 31 has one iron piece 43a (FIG. 15B) or two iron pieces 43a and 43b (FIG. 15A). The instruction unit 32 has two coils 42a and 42b. As the coils 42a and 42b, for example, general-purpose coil elements of several μH to several hundred mH can be used. As the iron pieces 43a and 43b, in addition to iron, a simple substance such as nickel, cobalt, manganese, chromium or an alloy-based ferromagnetic material, an alloy-based ferromagnetic material added with aluminum, copper, tungsten, samarium, neodymium, silicon, tellurium, etc. Alternatively, a sintered body such as ferrite can be used. Here, an on signal or an off signal is output using the fact that the inductance changes by bringing an iron piece closer to the coil. For example, if the inductance of the coil is about 10 mH, the inductance is reduced by about 10% when the iron piece is brought close to a distance of 1 mm (conversely, the inductance increases when a ferromagnetic material having a large electric resistance such as ferrite is brought close to the iron piece instead. ). It is determined whether the rise time of the voltage across each coil when a current pulse is applied to each coil is delayed from a preset time. When both the coils 42a and 42b are opposed to the iron pieces 43a and 43b as shown in FIG. 15A, the inductances of the coils 42a and 42b are both at the low level, and as shown in FIG. When only 42b faces the iron piece 43b, the inductance of the coil 42a is at a high level, and the inductance of the coil 42b is at a low level.

  In the configuration example shown in FIGS. 16A and 16B, the instruction unit 31 has one magnet piece 45a (FIG. 16B) or two magnet pieces 45a and 45b (FIG. 16A). The instruction unit 32 includes two magnetic sensors 44a and 44b. As the magnet pieces 45a and 45b, carbon steel, tungsten steel, KS steel (permanent magnet steel), alloy magnets such as aluminum, copper, nickel and cobalt, or rare earth cobalt magnets can be used. As the magnetic sensors 44a and 44b, for example, semiconductor magnetic sensors such as Hall elements can be used. As shown in FIG. 16A, when the magnetic sensors 44a and 44b are opposed to the magnet pieces 45a and 45b, the magnetic fields detected by the magnetic sensors 44a and 44b are stronger than preset values. On the other hand, when only the magnetic sensor 44b faces the magnet piece 45b as shown in FIG. 16B, the magnetic field detected by the sensor 44a is weaker than a preset value, and the magnetic field detected by the sensor 44b is Stronger than the set value.

  In the configuration example shown in FIG. 17A, the instruction unit 31 has a reflecting surface 48, and the instruction unit 32 has a light emitting element 46 and a light receiving element 47. As the light emitting element 46, for example, a light emitting diode or a light bulb can be used. As the light receiving element 47, for example, a photodiode, a phototransistor, a cadmium cell, or a solar battery can be used. The reflecting surface 48 only needs to be stable over time when the specular reflectance of visible light is in the range of 0 to 1.0, and may be paper, resin, metal, glass, tile, painting, or the like. Further, a part of the casing of the fixing device 30 may be polished, or the incident angle of light to the light receiving element 47 may be changed. In this case, since the intensity of incident light on the light receiving element 47 changes depending on the reflectance of the reflecting surface 48, it is possible to determine whether the intensity of incident light is higher than a preset value.

  In the configuration example shown in FIG. 17B, the instruction unit 31 has four terminals 50a, 50b, 50c, and 50d, and the instruction unit 32 has four terminals 49a, 49b, 49c, and 49d. A load resistor 51a is connected to the terminals 50a and 50b, and a load resistor 51b is connected between the terminals 50c and 50d. The terminals 49a to 49d and 50a to 50d may be any material that conducts by contact, and may be a highly conductive material such as gold, silver, copper, nickel, and aluminum. However, in terms of corrosion resistance and cost, brass is used. Is preferred. As the load resistors 51a and 51b, general-purpose resistors of several Ω to several GΩ can be used. In this case, it is possible to determine whether or not the resistance values of the resistors 51a and 51b are larger than a preset resistance value by energizing between the terminals 49a and 49b and between the terminals 49c and 49d.

  In the configuration example shown in FIG. 17C, the instruction unit 31 has two coils 53a and 53b connected in series with the load resistors 54a and 54b, respectively, and the instruction unit 32 has two coils 52a and 52b. ing. As the coils 52a, 52b, 53a, 53b, for example, general-purpose coil elements of several μH to several hundred mH can be used. As the load resistors 54a and 54b, general-purpose resistors of several Ω to several GΩ can be used. In this case, since the inductance of the coils 52a and 52b varies depending on the winding direction or inductance of the coils 53a and 53b or the size of the load resistors 54a and 54b, the determination based on the magnitude of the inductance as described with reference to FIG. Is possible.

  Next, the operation of the image forming apparatus in this embodiment will be described. When the main power of the image forming apparatus is turned on, or when a part of the housing is opened / closed for attaching / detaching the fixing device 30 with the power turned on, the control unit 34 notifies the determination unit 33. A determination of the type of the fixing device 30 is given. The determination unit 33 transmits a determination signal to the detection unit 32. The detection unit 32 outputs the detection signal described with reference to FIGS. 12 to 17 based on the instruction unit 31 of the fixing device 30 attached to the image forming apparatus. The determination unit 33 determines whether it is a fixing device (1) capable of fixing a borderless image or a normal fixing device (0) based on the determination criteria described below, and outputs the determination result to the control unit 34. Based on the signal from the determination unit 33, the control unit 34 permits borderless printing only when the fixing device is capable of fixing a borderless image.

  Tables 1 to 5 below show examples of determination in the determination unit 33.

  Table 1 corresponds to the configuration examples of FIGS. 12 and 13, and the switch SW1 corresponds to the switch 35a in FIG. 12 (or the switch 37a in FIG. 13). The switch SW2 corresponds to the switch 35b in FIG. 12 (or the switch 37b in FIG. 13). The determination unit 33 determines that the fixing device is a normal fixing device when the outputs from the switches SW1 and SW2 are both off signals, and there is no edge when the outputs from the switches SW1 and SW2 are an on signal and an off signal, respectively. It is determined that the fixing device can fix the image.

  Table 2 corresponds to the configuration example of FIG. 14 or FIG. 17A, and the determination unit 33 determines that the incident light intensity of the light receiving element 40 (47) is larger than a predetermined value set in advance. When the strength is less than a predetermined value, the fixing device is determined to be capable of fixing a borderless image.

  Table 3 corresponds to the configuration example of FIG. 15 or FIG. 17C, and the inductance Z1 is the inductance of the coil 42a in FIG. 15 (or the coil 52a in FIG. 17C). The inductance Z2 is the inductance of the coil 42b in FIG. 15 (or the coil 52b in FIG. 17C). When both the inductances Z1 and Z2 are at the low level, the determination unit 33 determines that the image is a normal fixing device, and when the inductances Z1 and Z2 are at the high level and the low level, respectively, the borderless image can be fixed. Judged as a fixing device.

  Table 4 corresponds to the configuration example of FIG. 16, and the magnetic fields G1 and G2 are magnetic fields detected by the magnetic sensors 44a and 44b in FIG. 16, respectively. When the magnetic fields G1 and G2 are stronger than a predetermined value, the determination unit 33 determines that the fixing device is a normal fixing device. When the magnetic field G1 is weaker than the predetermined value and the magnetic field G2 is stronger than the predetermined value, the determination unit 33 It is determined that the fixing device is capable of fixing an image without an image.

  Table 5 corresponds to the configuration example of FIG. 17B, and the resistors R1 and R2 correspond to the resistance values of the resistors 51a and 51b, respectively. The determination unit 33 determines that the fixing device is a normal fixing device when both of the resistors R1 and R2 are at the low level, and can fix the borderless image when the resistor R1 is at the high level and the resistor R2 is at the low level. Judged as a fixing device.

  As described above, according to the present embodiment, it is determined whether or not the fixing device in the image forming apparatus supports the fixing of the borderless image, and it is determined that the fixing of the borderless image is supported. Only in that case borderless printing is allowed. Therefore, for example, when a fixing device capable of fixing a borderless image is prepared as an option for an image forming apparatus equipped with a normal fixing device as a standard, the user can perform borderless printing while wearing the normal fixing device. It is possible to prevent troubles such as fixing failure and winding of the recording medium.

  The present invention can be applied to an image forming apparatus such as a copying machine, a printer, or a facsimile machine that forms a monochrome image or a color image of two or more colors.

1 is a diagram illustrating a basic configuration of a fixing device according to a first embodiment of the present invention. FIG. 2 is a diagram illustrating a configuration example (a) of a fixing roller, a configuration example (b) of a pressure roller, and a nip portion (c) of both rollers of the fixing device illustrated in FIG. The figure which shows the other example (a) of the basic composition of the fixing device concerning a 1st embodiment of the present invention, the example (a) of the fixing belt of the fixing device shown in Drawing 3 (a), and other examples It is a figure which shows (b). It is the schematic for demonstrating the measuring method of adhesive force. It is a graph which shows the result of having measured the relationship between adhesive force and the wax content in a toner, changing release agent application amount. 6 is a graph showing the results of measurement of the relationship between the amount of margin required to separate the leading edge of the recording medium from the fixing roller and the adhesion force by changing the hardness difference between the fixing roller and the pressure roller. 6 is a graph showing changes in fixing characteristics with respect to the surface roughness of a release layer of a fixing roller and a release agent coating amount. It is a figure which shows the principal part of the fixing device which concerns on the 2nd Embodiment of this invention. 6 is a timing chart illustrating an operation of a fixing device according to a second embodiment of the present invention. It is a graph for demonstrating the effect by the 2nd Embodiment of this invention. It is a figure which shows the basic composition of the image forming apparatus which concerns on the 3rd Embodiment of this invention. FIG. 12 is a diagram illustrating a configuration example of a detection unit and an instruction unit in the image forming apparatus illustrated in FIG. 11. FIG. 12 is a diagram illustrating another configuration example of a detection unit and an instruction unit in the image forming apparatus illustrated in FIG. 11. FIG. 12 is a diagram illustrating another configuration example of a detection unit and an instruction unit in the image forming apparatus illustrated in FIG. 11. FIG. 12 is a diagram illustrating another configuration example of a detection unit and an instruction unit in the image forming apparatus illustrated in FIG. 11. FIG. 12 is a diagram illustrating another configuration example of a detection unit and an instruction unit in the image forming apparatus illustrated in FIG. 11. FIG. 12 is a diagram illustrating another configuration example of a detection unit and an instruction unit in the image forming apparatus illustrated in FIG. 11.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,8 Fixing roller, 2,9 Pressure roller, 4,14,26 Release agent application member, 5,13 Temperature detection sensor, 6,15 Recording medium, 7,16 Toner, 11 Heating roller, 12 Fixing belt, 17 Metal core part, 18 elastic part, 19 release agent layer, 20 metal core part, 21 elastic part, 23 solenoid, 25 pressure spring, 27 support member, 29 control part, 30 fixing device, 31 indicating part, 32 detection part, 33 Judgment part, 34 control part.

Claims (13)

A fixing member;
A heat source for heating the fixing member;
A pressure member that is pressed against the fixing member to form a nip portion with the fixing member;
A release agent supply means for supplying a release agent to the fixing member or the pressure member,
In the fixing device for fixing the toner image to the recording medium by pressurizing and heating the recording medium carrying the toner image in the nip portion.
The wax content of the toner is A (parts by weight),
When the amount of the release agent applied to the fixing member or the pressure member by the release agent supply means is B (mg / sheet) per A4 size recording medium,
A fixing device in which the following expressions (1) to (3) are satisfied.
0 ≦ A ≦ 20 (1)
0 ≦ B ≦ 1.0 (2)
8 ≦ (A + 12 × B) ≦ 32 (3)   2. The fixing device according to claim 1, wherein the toner image is formed without leaving a margin on the outer periphery of the recording medium or so that the margin is within 2 mm from the outer periphery.   The fixing device according to claim 1, wherein the fixing member has a release layer on a surface thereof. 4. The fixing device according to claim 1, wherein the following expressions (4) and (5) are satisfied when the surface roughness of the fixing member is Rz (μm): 5.
0 <Rz ≦ 1.0 (4)
0 <Rz / B ≦ 1.0 (5) The following formulas (6) and (7) are satisfied, where C is an Asker C hardness on the surface of the fixing member and D is an Asker C hardness on the surface of the pressure member. The fixing device according to any one of 1 to 4.
70 ≦ C ≦ 95 (6)
−20 ≦ D−C ≦ 25 (7)   6. The fixing device according to claim 1, wherein a force necessary to peel the recording medium that has passed through the nip portion from the surface of the fixing member is 450 gf or less.   The fixing device according to claim 1, wherein the fixing member is a roller-shaped member.   The fixing device according to claim 1, wherein the fixing member is a belt-shaped member.   The said release agent application | coating member is a roller provided with the porous surface layer, Comprising: The release agent is hold | maintained in the hole, The any one of Claim 1 thru | or 8 characterized by the above-mentioned. Fixing device.   The fixing device according to claim 1, wherein the recording medium carries an unfixed toner image of two or more colors.   11. The fixing according to claim 1, further comprising a separation contact mechanism that causes the release agent application member to abut against or separate from the fixing member or the pressure member. apparatus.   12. An instruction unit that indicates a fixing device that supports marginless printing that does not leave a margin on the outer periphery of the recording medium or limits the margin to a certain area from the outer periphery. The fixing device according to claim 1. A detection unit that detects the type of the fixing device according to claim 12 based on the instruction unit, and outputs a detection signal corresponding to the type.
A determination unit for determining a type of the fixing device based on the detection signal;
A control unit that permits or prohibits borderless printing based on the determination result of the determination unit, and
The image forming apparatus, wherein the control unit permits borderless printing only when the determination unit determines that the fixing device is compatible with the borderless printing.

Images